On the Internet, a search engine is a coordinated set of programs that can include: a spider, a program that generates an index, and a program that receives a search request. A spider (also called a “crawler” or a “bot”) goes to every page or representative pages on a searchable Web site and reads it, using hypertext links on each page to discover and read a site's related pages. A catalog is a program that generates an index from the pages that have been read by the spider. The program that receives a search request compares it to the entries in the index and returns results, often to a graphical user interface (GUI), e.g., a browser, for display to a user. Example search engines, such as Lycos, Google, Yahoo, and AltaVista, index the content of a large portion of the Web and provide results to a user.